To investigate the resistance of the wire

We plan to discover whether the length of a piece of wire affects the overall resistance, of a metre long piece of wire.

Prediction

I predict that if I increase the wire length the resistance will be greater because the electrons have a greater distance and longer time to travel giving a greater probability of colliding with the wire atoms. This is the cause of resistance and where electrical energy is turned into heat energy.

Electricity flows in metals. Metal wires are made up of millions of tiny metal crystals. Each crystals atom is arranged in a regular pattern. The metals are full of free electrons that do not stick to any particular atom. They fill the space between the atoms in the metal. There is an electric current when these electrons move.

Equipment

The equipment used in this experiment:-

1x switch

1 x Ammeter

1 x Voltmeter

2x Batteries

1 x meter ruler

1m of resistance wire.

6 leads

Step by Step

All things need to be kept the same in an experiment except the one key variable, in this case the length of the wire. That will change every time I record another reading. To make the experiment a fair test I need to keep the same piece of wire, because different wires have different resistance, use the same connecting wires for the same reason. I will disconnect the circuit every time so the wires wont heat up. If the wires heat up then the atoms gain more kinetic energy increasing the resistance. Every component of the experiment as to be kept the same apart from the length of the wire this is because different components will have different resistance.

Knowledge

In 1899 J.J Thomson discovered electrons. Moving electrons are an electric current. Electricity flows in metals. Metal wires are made of millions of tiny metal crystals Each crystal’s atoms are arranged in a regular pattern. They are free electrons and don’t stick to any particular atom.

The diagram above shows how an electric current works. A potential difference makes the free electrons move along.

I don’t have enough results to support a firm conclusion, to firmly support a conclusion, I would need to perform the experiment in various ways, e.g. change the thickness of the wire and could maybe use different types of wire. I also could do more varying lengths. However I have looked at other group’s results and I can confirm that every other group had similar results and came to the same conclusion.

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All of these precautions were taken in order to maximize the reliability and accuracy of the recorded data and to reduce the chance of any outliers (anomalous readings). The safety of the experiment was purposefully kept to a maximum. The power packs had a block on them to prevent a voltage higher than 10v.

I also decided that it was unnecessary for me to have a voltmeter in my circuit since the voltage was being kept constant. In my preliminary work, it was not necessary for me to find a suitable value for the length of wire used when investigating the effect of cross-sectional